1. Field of the Invention
The invention relates to a valve device.
2. Description of Related Art
Fuel cell vehicles are provided with a valve device configured to control the supply of hydrogen gas from a gas tank to a fuel cell and to control the interruption of the supply of the hydrogen gas from the gas tank to the fuel cell. Examples of such a valve device include a valve device described in Japanese Patent Application Publication No. 2011-89569 (JP 2011-89569 A). The valve device described in JP 2011-89569 A includes a body having a supply passage communicated with a gas tank, and a solenoid valve accommodated in the body. The solenoid valve includes: a tubular sleeve having a flow passage communicated with the supply passage of the body; an opening-closing portion that opens and closes the flow passage in the sleeve; and a driving portion that drives the opening-closing portion to open or close the flow passage. A downstream-side opening of the flow passage in the sleeve is located inside the body. An outlet passage that extends from the opening of the sleeve to an outer surface of the body is formed in the body. With this configuration, the high-pressure hydrogen gas in the gas tank is introduced into the solenoid valve through the supply passage of the body. Then, the gas that has passed through the opening-closing portion of the solenoid valve flows through the flow passage of the sleeve and the outlet passage of the body. The gas is then delivered from an opening of the outer surface of the body to be supplied to a fuel cell. Seal members are disposed between an outer wall surface of the sleeve and an inner wall surface of the body. The seal members prevent the gas in the supply passage from flowing into the outlet passage through a clearance between the sleeve of the solenoid valve and the body.
In the valve device described in JP 2011-89569 A, the gas pressure in the supply passage of the body is usually higher than the gas pressure in the outlet passage of the body. Thus, a pressure (positive pressure) corresponding to the differential pressure is applied to the seal members. However, a pressure that is not a positive pressure may be applied to the seal members, due to the fluctuations of the gas pressure in the outlet passage. Examples of a pressure that is not a positive pressure include a pressure (counter pressure) that is generated, for example, when the gas pressure in the outlet passage becomes higher than the gas pressure in the supply passage. If such a counter pressure is applied to the seal members, a heavy load is placed on the seal members. This may be a factor of reduction in the useful life of the seal members, and may cause damages to components of the solenoid valve.